Refactor scripts arguments handling (#456)

- remove the use of environment variables to get directory paths,
- make use of arguments / argparse instead of environment variables in `update.py` and `report.py`,
- automatically guess the data directory in `latest.py` based on the script's location,
- propagate log level to auto scripts,
- move `list_configs_from_argv` from `endoflife` module to `releasedata` module,
- use `list_products` in `latest.py` to load the product's frontmatters.

src/google-kubernetes-engine.py

@@ -1,6 +1,6 @@
 import re
 
-from common import dates, endoflife, http, releasedata
+from common import dates, http, releasedata
 
 # https://regex101.com/r/zPxBqT/1
 VERSION_PATTERN = re.compile(r"\d.\d+\.\d+-gke\.\d+")
@@ -11,7 +11,7 @@ URL_BY_PRODUCT = {
     "google-kubernetes-engine-rapid": "https://cloud.google.com/kubernetes-engine/docs/release-notes-rapid",
 }
 
-for config in endoflife.list_configs_from_argv(): # noqa: B007 multiple JSON produced for historical reasons
+for config in releasedata.list_configs_from_argv(): # noqa: B007 multiple JSON produced for historical reasons
     for product_name, url in URL_BY_PRODUCT.items():
         with releasedata.ProductData(product_name) as product_data:
             html = http.fetch_html(url)